75,294 research outputs found
BILIPROTEINS FROM THE BUTTERFLY Pieris brassicae STUDIED BY TIME-RESOLVED FLUORESCENCE AND COHERENT ANTI-STOKES RAMAN SPECTROSCOPY
The fluorescence decay time of the biliverdin IX7 chromophore present in biliproteins isolated from Pieris brassicae is determined to be 44 ± 3 ps. This value suggests a cyclic helical chromophore structure. The vibrational frequencies determined by CARS-spectroscopy are compared with those of model compounds. The data confirm that the chromophore in the protein-bound state adopts a cyclic-helical, flexible conformation
Pressure effects on the superconducting properties of YBa_2Cu_4O_8
Measurements of the magnetization under high hydrostatic pressure (up to 10.2
kbar) in YBa_2Cu_4O_8 were carried out. From the scaling analysis of the
magnetization data the pressure induced shifts of the transition temperature
T_c, the volume V and the anisotropy \gamma have been obtained. It was shown
that the pressure induced relative shift of T_c mirrors essentially that of the
anisotropy. This observation uncovers a novel generic property of anisotropic
type II superconductors, that inexistent in the isotropic case.Comment: 4 pages, 3 figure
Evidence for charged critical behavior in the pyrochlore superconductor RbOs2O6
We analyze magnetic penetration depth data of the recently discovered
superconducting pyrochlore oxide RbOs2O6. Our results strongly suggest that in
RbOs2O6 charged critical fuctuations dominate the temperature dependence of the
magnetic penetration depth near Tc. This is in contrast to the mean-field
behavior observed in conventional superconductors and the uncharged critical
behavior found in nearly optimally doped cuprate superconductors. However, this
finding agrees with the theoretical predictions for charged criticality and the
charged criticality observed in underdoped YBa2Cu3O6.59.Comment: 5 pages, 4 figure
Lifting of Quantum Linear Spaces and Pointed Hopf Algebras of order p^3
We propose the following principle to study pointed Hopf algebras, or more
generally, Hopf algebras whose coradical is a Hopf subalgebra. Given such a
Hopf algebra A, consider its coradical filtration and the associated graded
coalgebra grad(A). Then grad(A) is a graded Hopf algebra, since the coradical
A_0 of A is a Hopf subalgebra. In addition, there is a projection \pi: grad(A)
\to A_0; let R be the algebra of coinvariants of \pi. Then, by a result of
Radford and Majid, R is a braided Hopf algebra and grad(A) is the bosonization
(or biproduct) of R and A_0: grad(A) is isomorphic to (R # A_0). The principle
we propose to study A is first to study R, then to transfer the information to
grad(A) via bosonization, and finally to lift to A. In this article, we apply
this principle to the situation when R is the simplest braided Hopf algebra: a
quantum linear space. As consequences of our technique, we obtain the
classification of pointed Hopf algebras of order p^3 (p an odd prime) over an
algebraically closed field of characteristic zero; with the same hypothesis,
the characterization of the pointed Hopf algebras whose coradical is abelian
and has index p or p^2; and an infinite family of pointed, non-isomorphic, Hopf
algebras of the same dimension. This last result gives a negative answer to a
conjecture of I. Kaplansky.Comment: AmsTeX, 28 pages. To be published in J. of Algebr
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